Compounds and methods for treating cancer

ABSTRACT

The present invention provides a method of treating cancer involving administering an insulin-like growth factor-1 receptor (IGF-1 receptor) agonist and an anti-cancer chemotherapeutic agent. Also provided are compounds for treating cancer comprising an IGF-1-receptor ligand coupled to an anti-cancer chemotherapeutic agent. Also provided are compounds for treating cancer comprising an insulin-receptor ligand coupled to an anti-cancer chemotherapeutic agent.

This application claims priority as a continuation-in-part applicationunder 35 U.S.C. §120 from international application no.PCT/US2004/034704, filed Oct. 21, 2004 and U.S. provisional patentapplication Ser. No. 60/513,048, filed Oct. 21, 2003, both of which areincorporated by reference.

BACKGROUND

Currently 1.3 million people are diagnosed with cancer each year in theUnited States alone, and over 500,000 die. Treatment for most types ofcancers includes chemotherapy. Chemotherapy drugs are administeredsystemically and attack all cells of the body, particularly dividingcells, not just cancer cells. Thus, side effects from chemotherapy drugsare often severe. These include anemia, nausea, hair loss, and immunesuppression, including neutropenia, due to depletion of white bloodcells. The side effects often limit the dose of chemotherapy agents thatcan be administered.

Cancer cells are obligately glycolytic. That is, they must consumeglucose for their energy needs; and they consume it anaerobically, whichyields less energy than aerobic respiration. As a consequence, cancercells must consume a large amount of glucose. Perhaps to assist withacquiring glucose, cancer cells from many types of cancer have beenobserved to have more insulin receptors than normal cells. (Ayre, S. G.,et al., 2000, Medical Hypotheses 55:330; Abita, J. F., et al., 1984,Leukemia Res. 8:213.) Recently, a method of cancer treatment termedinsulin potentiation therapy (IPT) that attempts to exploit the insulinreceptors of cancer cells has been introduced in the United States.(Ayre, S. G., et al., 2000, Medical Hypotheses 55:330.) The methodinvolves administering insulin to cancer patients, followed a short timelater by administering chemotherapy drugs. Lower doses of chemotherapydrugs are used, which reduces the side effects. It is purported that theinsulin somehow potentiates the effect of the chemotherapeutic agents onthe cancer cells, allowing the use of lower doses.

In vitro data is reported to show that when methotrexate is administeredwith insulin to breast cancer cells in tissue culture, the same percentcell killing is achieved with 10⁴ lower methotrexate concentrations thanwhen methotrexate is administered alone. (Alabaster, O., et al., 1981,Eur J. Cancer Clin. Oncol. 17:1223.) Methotrexate is a folic acidanalogue that leads to the depletion of tetrahydrofolate. Thisinterferes with thymidine and purine synthesis, and hence DNA synthesis.

Insulin does not greatly stimulate uptake of chemotherapeutic agents.One study has shown only a 2-fold stimulation of uptake of elipticine byMDA-MB-231 breast cancer cells when the cells were incubated withinsulin. (Oster, J. B., et al., 1981, Eur J. Cancer Clin. Oncol.17:1097.) Another study showed a 50% stimulation of uptake ofmethotrexate by breast cancer cells when the cells were incubated withinsulin. (Shilsky, R. L., et al., 1981, Biochem. Pharmacol. 30:1537.)Thus, the mechanism for insulin potentiation of methotrexatecytotoxicity must be primarily due to factors other than enhanceduptake.

Another receptor often found in greater numbers in cancer cells than innormal cells of the same tissue type is the insulin-type growth factor-1receptor (IGF-1 receptor or IGF-1R). IGF-1 is a peptide of 70 amino acidresidues having 40% identity with proinsulin. (Daughaday, W. H., et al.,1989, Endocrine Revs. 10:68.) Insulin and IGF-1 have somecross-reactivity with each other's receptor. (Soos, M. A., et al., 1993,Biochem. J. 290:419.) IGF-1 is secreted by the liver into thecirculatory system and stimulates growth of many cell types. IGF-1 isalso produced by many cell types throughout the body, including manycancers, for autocrine and paracrine effects. IGF-1 production isstimulated by growth hormone. (Stewart, C. H., e t al., 1996, Physiol.Revs. 76:1005; Yakar, S., et al., 2002, Endocrine 19:239.)

New methods to enhance the effectiveness of chemotherapy and/or toreduce the side effects of chemotherapy, for instance by reducing thedoses of chemotherapeutic agents used, are needed. In addition newanti-cancer chemotherapeutic agents are needed. Preferably the newagents would have lower side effects and/or be more effective in killingcancer cells than agents currently in use.

SUMMARY

Insulin has been shown in vitro to potentiate the effect of onechemotherapeutic agent against breast cancer cells, allowing killing ofthe cells with lower concentration of methotrexate. This effectpresumably depends on the cancer cells having insulin receptors. Mostlikely the enhancement of killing is because insulin stimulates cells todivide, and methotrexate, like most other chemotherapeutic agents, ismore toxic to dividing cells than non-dividing cells. It is known, forinstance, that rapidly growing tumors are more sensitive to chemotherapythan slow-growing ones. (Shackney, S. E., et al., 1978, Ann. Intern.Med. 89:107.) However, insulin and methotrexate were administeredseparately, and the insulin had little effect on increasing the uptakeof methotrexate by cancer cells.

By physically coupling chemotherapeutic agents to insulin or an insulinreceptor ligand, the uptake of the chemotherapeutic agents by the cancercells is increased. The coupled compounds bind to insulin receptors onthe cell surface, thus holding the chemotherapeutic agents on the cellsurface, where their uptake is greatly increased relative to the uptakeof a chemotherapeutic agent not coupled to insulin. The conjugates andthe receptors to which they bind are efficiently taken into the cell byreceptor-mediated endocytosis. (Schlessinger, J., et al., 1978, Proc.Nat'l Acad. Sci. USA 75:2659; Pilch, P. F., et al., 1983, J. Cell Biol.93:133; (Pozansky, M. J., et al., 1984, Science 223:1304.) Thechemotherapeutic agent will also be internalized and will be effectiveagainst the cancer cells. This is evidenced by the showing that amethotrexate-albumin conjugate is more effective than free methotrexatein treating a cancer implanted in mice. (Bures, L., et al., 1988,Neoplasma 35:329.) Because of the enhanced uptake into cancer cells, thecompounds containing insulin coupled to a chemotherapeutic agent killcancer cells more efficiently than free chemotherapeutic agent, evenwhen the free agent is administered in conjunction with insulin.

Uptake of the coupled chemotherapeutic agents into normal cells,however, is not increased as much, because normal cells have fewerinsulin receptors than neoplastic cells. Thus, the conjugate gives goodselectivity for cancer cells.

Insulin-chemotherapeutic agent conjugates also have the advantage ofstimulating cancer cells to divide, thus making them more sensitive tothe chemotherapeutic agents, which target dividing cells.

IGF-1 receptors are also overexpressed in most cancer cells.Furthermore, IGF-1 stimulates cancer cells to divide to an even greaterextent than insulin. (Stewart, C. H., et al., 1996, Physiol. Revs.76:1005; Yakar, S., et al., 2002, Endocrine 19:239.) IGF-1 and insulinalso cross-react to some degree with each other's receptors. Sincechemotherapeutic drugs generally act against dividing cells, stimulatingcancer cells to divide makes them more sensitive to chemotherapeuticagents.

Thus, coadministering IGF-1 with chemotherapeutic agents potentiates theeffect of the chemotherapeutic agents by stimulating cancer cells todivide, thus making them more sensitive to chemotherapeutic agents thatkill dividing cells. Furthermore, like insulin, IGF-1 can be coupled tochemotherapeutic agents so as to increase uptake of the chemotherapeuticagents into cancer cells, while having less effect on uptake into normalcells, which usually have fewer IGF-1 receptors.

Accordingly, the invention provides a compound for treating cancercomprising an anti-cancer chemotherapeutic agent linked to an insulinreceptor ligand, wherein the chemotherapeutic agent is not methotrexate.

Another embodiment of the invention provides a pharmaceuticalcomposition comprising: a compound comprising an anti-cancerchemotherapeutic agent linked to an insulin receptor ligand, wherein thechemotherapeutic agent is not methotrexate. The pharmaceuticalcomposition typically also includes a pharmaceutically acceptablediluent.

Another embodiment of the invention provides a method of treating cancerin a mammal, comprising: administering a compound containing ananti-cancer chemotherapeutic agent linked to an insulin receptor ligand,wherein the compound inhibits growth of the cancer in the mammal.

Another embodiment of the invention provides a method of inhibitinggrowth of cancer cells comprising: contacting the cancer cells with acompound containing an anti-cancer chemotherapeutic agent linked to aninsulin receptor ligand, wherein the compound inhibits the growth of thecancer cells, wherein the chemotherapeutic agent is not methotrexate.

Another embodiment of the invention provides a method of screening acompound for anti-cancer activity comprising: contacting a compoundcontaining a chemotherapeutic agent linked to an insulin receptor ligandwith cancer cells; and determining whether the compound inhibits growthof the cancer cells, wherein the chemotherapeutic agent is notmethotrexate.

Another embodiment of the invention provides a compound for treatingcancer comprising: an anti-cancer chemotherapeutic agent linked to aninsulin-like growth factor-1 (IGF-1) receptor ligand, wherein the IGF-1receptor ligand is not insulin. Preferably, the ligand has a bindingaffinity for the IGF-1 receptor greater than the binding affinity ofinsulin for the IGF-1 receptor. Preferably the IGF-1 receptor ligand hasa binding affinity for the IGF-1 receptor greater than for the insulinreceptor.

Another embodiment of the invention provides a pharmaceuticalcomposition comprising: a compound comprising an anti-cancerchemotherapeutic agent linked to an insulin-like growth factor-1 (IGF-1)receptor ligand; wherein the IGF-1 receptor ligand is not insulin. Thepharmaceutical composition typically also includes a pharmaceuticallyacceptable diluent.

Another embodiment of the invention provides a method of treating cancerin a mammal comprising: administering a compound containing ananti-cancer chemotherapeutic agent linked to an IGF-1 receptor ligand,wherein the compound inhibits growth of the cancer in the mammal,wherein the IGF-1 receptor ligand is not insulin.

Another embodiment of the invention provides a method of inhibiting thegrowth of cancer cells comprising contacting the cancer cells with acompound comprising an anti-cancer chemotherapeutic agent linked to anIGF-1 receptor ligand, wherein the compound inhibits the growth of thecancer cells, wherein the IGF-1 receptor ligand is not insulin.

Another embodiment of the invention provides a method of screening acompound for anti-cancer activity comprising: contacting cancer cellswith a compound containing an anti-cancer chemotherapeutic agent linkedto an IGF-1 receptor ligand; and determining whether the compoundinhibits growth of the cancer cells, wherein the IGF-1 receptor ligandis not insulin.

Another embodiment of the invention provides a method of treating cancerin a mammal, comprising: administering to the mammal an anti-cancerchemotherapeutic agent and an IGF-1 receptor agonist, wherein the IGF-1receptor agonist is not insulin.

Another embodiment of the invention provides a method of inhibitinggrowth of cancer cells comprising: contacting the cells with ananti-cancer chemotherapeutic agent and an IGF-1 receptor agonist;wherein the IGF-1 receptor agonist is not insulin, and wherein theanti-cancer chemotherapeutic agent is not doxorubicin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an SDS-PAGE analysis of the conjugateinsulin-methotrexate-A.

FIG. 2 is a plot showing the concentration dependence of in vitro growthinhibition of FSAII tumor cells by methotrexate and insulin-methotrexateconjugates.

FIG. 3 is a plot showing the relative abundance of insulin receptors andIGF-1 receptors on several malignant cell lines based on fluorescenceactivated cell sorting (FACS) using fluorescently labeled antibodiesagainst the receptors.

FIG. 4 is a plot showing the effects of methotrexate and aninsulin-methotrexate conjugate in inhibiting FSAII tumor growth in vivoin mice. Standard error bars are shown for the untreated control datapoints and low dose insulin-methotrexate conjugate data points.

FIG. 5 is a plot showing the effects of methotrexate and aninsulin-methotrexate conjugate in inhibiting LNCAP tumor growth in vivoin mice.

FIG. 6 is a plot showing the concentration dependence of in vitro growthinhibition of LNCAP tumor cells by methotrexate and aLONG-R3-IGF-1-methotrexate conjugate.

DETAILED DESCRIPTION

Definitions:

The term “anti-cancer chemotherapeutic agent” refers to a synthetic,biological, or semi-synthetic compound that is not an enzyme and thatkills cancer cells or inhibits the growth of cancer cells while havingless effect on non-cancerous cells.

The term “treating cancer” includes, e.g., preventing metastasis,inhibiting growth of a cancer, stopping the growth of cancer, or killingcells of a cancer.

The term “binding affinity” of a ligand for a particular receptor refersto the association constant K_(A) (the inverse of the dissociationconstant K_(D)) or to experimentally determined approximations thereof.

The term “anti-metabolite” refers to an anti-cancer chemotherapeuticagent that bears a structural similarity to a naturally occurringsubstance, interacts with enzymes as an inhibitor or a substrate, andinterferes with cellular processes. Examples include methotrexate,fluorouracil, floxuridine, fludarabine, mercaptopurine, thioguanine,cytarabine, azacytidine, cladribine, and pentostatin.

The term “agonist” refers to a ligand to the insulin receptor or IGF-1receptor that, when it binds to the receptor, activates the normalbiochemical and physiological events triggered by binding of the naturalligand for the receptor (i.e, insulin for the insulin receptor or IGF-1for the IGF-1 receptor). In particular embodiments, an agonist has atleast 20%, at least 30%, or at least 50% of the biological activity ofthe natural ligand. The activity of an insulin receptor ligand can bemeasured, for instance, by measuring the hypoglycemic effect (Poznansky,M. J., et al., 1984, Science 223:1304). The activity of aninsulin-receptor ligand or IGF-1-receptor ligand can be measured invitro by the measuring the extent of autophosphorylation of the receptorin response to ligand binding, as described in Satyamarthy, K., et al.,2001, Cancer Res. 61:7318. MAP kinase phosphorylation can also bemeasured for the IGF-1 receptor (Satyamarthy, K., et al., 2001, CancerRes. 61:7318).

The term “antagonist” refers to a ligand that has little or nostimulating activity when it binds to the receptor and that competeswith or inhibits binding of the natural ligand to the receptor. Inparticular embodiments, an antagonist has less than 20%, less than 10%,or less than 5% of the activity of the natural ligand (insulin for theinsulin receptor or IGF-1 for the IGF-1 receptor).

The “IGF-1 receptor” is also known in the literature as the type 1 IGFreceptor.

“Containing” as used herein is open-ended; i.e, it allows the inclusionof other unnamed elements and has the same meaning as “comprising.”

Description:

The invention provides a conjugate compound for treating cancercomprising: an anti-cancer chemotherapeutic agent linked to an insulinreceptor ligand. In particular embodiments, the anti-cancerchemotherapeutic agent is not methotrexate.

In particular embodiments, the insulin receptor ligand contains or isinsulin, IGF-1, or IGF-2. For instance, the insulin receptor ligand canbe a monomer of insulin, IGF-1, or IGF-2, or a polymer of insulin,IGF-1, or IGF-2 monomers. In other particular embodiments, the insulinreceptor ligand is or contains an antibody, e.g. a monoclonal antibodyor a polyclonal antibody.

In a specific embodiment, the insulin receptor ligand is not IGF-1.

Preferably the insulin receptor ligand has a higher binding affinity forthe insulin receptor than IGF-1. Preferably the insulin receptor ligandhas a higher binding affinity for the insulin receptor than it does forthe IGF-1 receptor.

The insulin receptor ligand can be an insulin receptor agonist orinsulin receptor antagonist. An agonist has the advantage that itstimulates the cells to divide, thus making them more sensitive tochemotherapeutic agents. However, an antagonist can also beadvantageous. Inactivation of the IGF-1 receptor has been shown topromote apoptosis. It is likely that inactivation of the insulinreceptor would have the same effect.

Examples of natural agonists of the insulin receptor are insulin, IGF-1,and IGF-2. Methods of identifying antagonist and agonist peptides forthe insulin receptor are disclosed in U.S. published patent application2004/0023887. Some examples of antagonist and agonist peptides are alsodisclosed.

Any suitable anti-cancer chemotherapeutic agent can be used in theconjugates of the invention and in the methods of treating cancer orinhibiting cancer cell growth by administering the agent and an IGF-1receptor agonist. For instance, in particular embodiments, thechemotherapeutic agent is mechlorethamine, cyclophosphamide, ifosfamide,melphalan, chlorambucil, thiotepa, hexamethylmelamine, busulfan,carmustine, lomustine, semustine, streptozocin, decarbazine,vincristine, vinblastine, etoposide, teniposide, paclitaxel, docetaxel,daunorubicin, idarubicin, doxorubicin, epirubicin, dactinomycin,plicamycin, mitomycin C, bleomycin, mitoxantrone, fluorouracil,floxuridine, fludarabine, mercaptopurine, thioguanine, cytarabine,azacytidine, cladribine, pentostatin, cisplatin, carboplatin, mitotane,procarbazine, or amsacrine.

In other particular embodiments, the chemotherapeutic agent ismechlorethamine, cyclophosphamide, ifosfamide, melphalan, chlorambucil,thiotepa, hexamethylmelamine, busulfan, carmustine, lomustine,semustine, streptozocin, decarbazine, vincristine, vinblastine,etoposide, teniposide, paclitaxel, docetaxel, daunorubicin, idarubicin,doxorubicin, epirubicin, dactinomycin, plicamycin, mitomycin C,bleomycin, mitoxantrone, methotrexate, fluorouracil, floxuridine,fludarabine, mercaptopurine, thioguanine, cytarabine, azacytidine,cladribine, or pentostatin.

In other particular embodiments, the anti-cancer chemotherapeutic agentis amsacrine, azacytidine, bleomycin, busulfan, capecitabine,carboplatin, carmustine, chlorambucil, cisplatin, cladribine,cyclophosphamide, cytarabine, dactinomycin, daunorubicin, decarbazine,docetaxel, doxorubicin, epirubicin, estramustine, etoposide,floxuridine, fludarabine, fluorouracil, gemcitabine, hexamethylmelamine,idarubicin, ifosfamide, irinotecan, lomustine, mechlorethamine,melphalan, mercaptopurine, methotrexate, mitomycin C, mitotane,mitoxantrone, oxaliplatin, paclitaxel, pemetrexed, pentostatin,plicamycin, procarbazine, ralitrexed, semustine; streptozocin,temozolamide, teniposide, thioguanine, thiotepa, topotecan,trimitrexate, valrubicin, vincristine, vinblastine, vindestine, orvinorelbine.

In particular embodiments, the anti-cancer chemotherapeutic agent is anantimetabolite. For instance, it can be methotrexate, fluorouracil,floxuridine, fludarabine, mercaptopurine, thioguanine, cytarabine,azacytidine, cladribine, pentostatin, pemetrexed, raltitrexed,trimetrexate, capecitabine, or gemcitabine.

In particular embodiments, the anti-cancer chemotherapeutic agent ismethotrexate.

In other particular embodiments, the anti-cancer chemotherapeutic agentis an alkylating agent, e.g., mechlorethamine, cyclophosphamide,ifosfamide, melphalan, chlorambucil, thiotepa, hexamethylmelamine,busulfan, carmustine, lomustine, semustine, streptozocin, decarbazine,estramustine, streptozocin, decarbazine, or temozolamide.

In particular embodiments, the anti-cancer chemotherapeutic agent is anantibiotic, e.g., bleomycin, dactinomycin, daunorubicin, doxorubicin,epirubicin, idarubicin, mitomycin, mitoxantrone, or valrubicrin.

In particular embodiments, the anti-cancer chemotherapeutic agent isdoxorubicin.

In particular embodiments, the anti-cancer chemotherapeutic agent isdocetaxel, paclitaxel, vinblastine, vincristine, vindesine, vinorelbine,irinotecan, topotecan, etoposide, or teniposide.

In particular embodiments, the anti-cancer chemotherapeutic agent hasgreater activity against cells in S phase of the cell cycle, than inother phases. In other embodiments, the agent has greater activityagainst cells in G2 phase. In other embodiments, the agent has greateractivity against cells in M phase. These agents are particularlysuitable, because IGF-1 has been shown to increase the proportion ofcells S phase, G2 phase, and M phase. (Ciftci, K., et al., 2003, JPharmacy and Pharmacology 55:1135.) Insulin and other insulin receptoragonists are believed to have the same effect.

In particular embodiments, the anti-cancer chemotherapeutic agent islinked to the insulin receptor ligand or IGF-1 receptor ligand by ahydrolyzable linkage, e.g., a linkage that comprises a Schiff base orimidoamide bond. In other particular embodiments, the hydrolyzablelinkage comprises an amide, phosphoester, sulfoester, ester, orglycoside bond.

In some embodiments, the anti-cancer chemotherapeutic agent is linked tothe insulin receptor ligand or IGF-1 receptor ligand by a direct bond,e.g, an amide bond between an amine group of the insulin receptor ligandand a carboxyl of the chemotherapeutic agent, or vice versa. In otherembodiments the anti-cancer chemotherapeutic agent is linked to theinsulin receptor ligand by a linker moiety.

In specific embodiments, the linker moiety comprises a phosphonyldioxy,sulfonyldioxy, sugar, deoxysugar, or peptide.

In particular embodiments where the insulin-receptor ligand is insulin,the chemotherapeutic agent is linked to insulin through an amino groupof insulin. In particular embodiments where the IGF-1 receptor ligand isIGF-1, the chemotherapeutic agent is linked to IGF-1 through an aminogroup of IGF-1. Likewise, the chemotherapeutic agent can be linked toany protein (e.g., IGF-2) or non-protein ligand that has one or moreamino groups through one or more of the amino groups.

In particular embodiments where the insulin-receptor ligand is insulin,the chemotherapeutic agent is linked to insulin through a carboxyl groupof insulin. In particular embodiments where the IGF-1 receptor ligand isIGF-1, the chemotherapeutic agent is linked to IGF-1 through a carboxylgroup of IGF-1. Likewise, the chemotherapeutic agent can be linked toany protein (e.g., IGF-2) or non-protein ligand that has one or morecarboxyl groups through one or more of the carboxyl groups.

In particular embodiments where the insulin receptor ligand or IGF-1receptor ligand is a protein (e.g., insulin, IGF-1, or IGF-2), thechemotherapeutic agent is linked to the protein through an amino acidside chain of the protein. The amino acid side chain can be, forinstance, a lysine side chain. In other particular embodiments, thechemotherapeutic agent is linked to the protein ligand through anamino-terminal alpha-amino group or a carboxyl-terminal alpha-carboxylgroup.

In particular embodiments of the conjugates, the ratio ofchemotherapeutic agent to insulin receptor ligand or IGF-1 receptorligand is approximately 1:1 (e.g., between 0.5 and 1.5 to 1). In otherembodiments, the ratio of chemotherapeutic agent to insulin receptorligand or IGF-1 receptor ligand is 2 or more (i.e., on average eachligand molecule has two or more chemotherapeutic molecules conjugated toit).

In particular embodiments of the method of treating cancer, the mammalis a human. In other particular embodiments, the mammal is anexperimental animal, such as a mouse.

In particular embodiments of the methods of treating cancer, the canceris lung cancer (e.g., small cell), prostate cancer, colorectal cancer,breast cancer, pancreatic cancer, leukemia, liver cancer, stomachcancer, ovarian cancer, uterine cancer, testicular cancer, brain cancer,non-Hodgkin's lymphoma, Hodgkin's lymphoma, Ewing's sarcoma,osteosarcoma, neuroblastoma, rhabdomyosarcoma, melanoma, or braincancer.

The invention also provides a method of inhibiting growth of cancercells involving: contacting the cancer cells with a compound containingan anti-cancer chemotherapeutic agent linked to an insulin receptorligand, wherein the compound inhibits the growth of the cancer cells.The invention also provides a method of inhibiting growth of cancercells involving contacting the cancer cells with a compound containingan anti-cancer chemotherapeutic agent linked to an IGF-1 receptorligand.

In some embodiments of the methods of inhibiting the growth of cancercells, the conjugate compound kills at least a portion of the cancercells.

In specific embodiments of the methods of inhibiting the growth ofcancer cells, the contacting can be in vitro or in vivo.

In specific embodiments of the methods of inhibiting the growth ofcancer cells, the cancer cells can include lung cancer, prostate cancer,colorectal cancer, breast cancer, pancreatic cancer, leukemia, livercancer, stomach cancer, ovarian cancer, uterine cancer, testicularcancer, brain cancer, non-Hodgkin's lymphoma, Hodgkin's lymphoma,Ewing's sarcoma, osteosarcoma, neuroblastoma, rhabdomyosarcoma,melanoma, or brain cancer cells.

The method of treating cancer in a mammal and the method of inhibitinggrowth of cancer cells involving use of a compound comprising ananti-cancer chemotherapeutic agent linked to an insulin receptor ligandnormally involve cancers where the cells have insulin receptors.Preferably, the cancer cells are also stimulated to proliferate byinsulin or the insulin receptor ligand.

Likewise, the method of treating cancer in a mammal and the method ofinhibiting growth of cancer cells involving use of a compound comprisingan anti-cancer chemotherapeutic agent linked to an IGF-1 receptor ligandnormally involve cancers where the cells have IGF-1 receptors.Preferably, the cancer cells are also stimulated to proliferate by IGF-1or by the IGF-1 receptor ligand.

In the methods of screening a conjugate compound by contacting thecompound with cancer cells and determining whether the compound inhibitsthe growth of the cancer cells, the contacting can be in vitro or invivo.

In particular embodiments, the compound kills at least a portion of thecancer cells. In particular embodiments, the screening involvesdetermining whether the compound kills the cancer cells.

The invention provides a conjugate compound for treating cancercomprising: an anti-cancer chemotherapeutic agent linked to an IGF-1receptor ligand, wherein the IGF-1 receptor ligand is not insulin.

In particular embodiments, the IGF-1 receptor ligand is or containsIGF-1. In other embodiments, it is or contains IGF-2. In someembodiments, the ligand comprises IGF-1 or IGF-2. For instance, theligand can be an IGF-1 or IGF-2 monomer or a polymer of IGF-1 monomersor IGF-2 monomers.

Preferably, the IGF-1 receptor ligand has a binding affinity for theIGF-1 receptor greater than insulin. Preferably, the IGF-1 receptorligand has a binding affinity for the IGF-1 receptor greater than forthe insulin receptor.

In particular embodiments, the IGF-1 receptor ligand is or contains anantibody, e.g., a monoclonal antibody or a polyclonal antibody.

The IGF-1 receptor ligand can be an IGF-1 receptor agonist orantagonist. An agonist has the advantage that it stimulates the cells todivide, thus making them more sensitive to the anti-cancerchemotherapeutic agent. However, an antagonist can also be advantageous.Inactivation of the IGF-1 receptor has been shown to promote apoptosis,so an antagonist will promote apoptosis.

Examples of agonist and antagonist peptide ligands to the IGF-1receptor, and methods of identifying agonist and antagonist peptideligands to the IGF-1 receptor, are disclosed in U.S. published patentapplications 2004/0023887 and 2003/0092631. One antagonist is thepeptide SFYSCLESLVNGPAEKSRGQWDGCRKK (SEQ ID NO:3).

Other examples of IGF-1 receptor agonists include variants of IGF-1 thatactivate the receptor but have reduced affinity for the soluble IGF-1binding proteins, such as those disclosed in U.S. Pat. No. 4,876,242.IGF binding proteins are natural serum proteins that bind to IGF-1,holding it in circulation and extending its biological half-life. It maybe advantageous for the IGF-1 receptor ligands of this invention,particularly agonists co-administered with chemotherapeutic agents asseparate molecules, to have reduced binding to the IGF-1 bindingproteins, because that reduced binding would accelerate the release ofthe agent to bind to the IGF-1 receptors. Thus, in some embodiments, theIGF-1 receptor ligand or agonist has reduced affinity for soluble IGF-1binding proteins, as compared to native IGF-1.

One preferred variant IGF-1 for use in the methods and conjugates of theinvention is LONG-R3-IGF-1 (Francis, G. L., et al. 1992, J. Mol.Endocrinol. 8:213-223; Tomas, F. M. et al., 1993, J. Endocrinol.137:413-421).

Preferably, the IGF-1 receptor ligand with reduced affinity for solubleIGF-1 binding proteins has at least 5-fold, more preferably at least10-fold, more preferably still at least 100-fold lower binding affinityfor soluble IGF-1 binding proteins than wild-type IGF-1. Bindingaffinity for the soluble IGF-1 binding proteins can be measured by acompetition binding assay against labeled IGF-1 (e.g., I-125-IGF-1),using a mixture of purified IGF-1 binding proteins or rat L6myoblast-conditioned medium (a naturally produced mixture of IGF-1binding proteins), as described in Francis, G. L., et al. (1992, J. Mol.Endocrinol. 8:213-223); Szabo, L. et al. (1988, Biochem. Biophys. Res.Commun. 151:207-214); and Martin, J. L. et al. (1986, J. Biol. Chem.261:8754-8760). Preferably, the variant IGF-1 has an IC₅₀ in acompetition binding assay against labeled wild-type IGF-1 for binding tosoluble IGF-1 binding proteins in L6 myoblast-conditioned medium ofgreater than 10 nM, more preferably greater than 100 nM.

Preferably, the variant IGF-1 with reduced affinity for soluble IGF-1binding proteins has affinity for the IGF-1 receptor that is close towild-type IGF-1 (e.g., less than 30-fold greater than wild-type IGF-1,more preferably less than 10-fold greater than wild-type IGF-1). Inspecific embodiments, the variant IGF-1 has an IC₅₀ in a competitionbinding assay against labeled wild-type IGF-1 for binding to IGF-1receptors (e.g., on MCF-7 cells) of less than 50 nM, more preferablyless than 10 nM, more preferably still less than 5 nM, more preferablystill less than 3 nM). This assay is described in Ross, M. et al. (1989,Biochem. J. 258:267-272) and Francis, G. L., et al. (1992, J. Mol.Endocrinol. 8:213-223).

The invention also provides a method of treating cancer in a mammal,comprising: administering to the mammal an anti-cancer chemotherapeuticagent and an IGF-1 receptor agonist, wherein the IGF-1 receptor agonistis not insulin.

In a specific embodiment, the IGF-1 receptor agonist has a bindingaffinity for the IGF-1 receptor greater than insulin.

Normally the method involves cancers where the cells have IGF-1receptors. Preferably, the cancer cells are also stimulated toproliferate by IGF-1 or by the IGF-1 receptor agonist.

In a particular embodiment of the method, the chemotherapeutic agent isnot doxorubicin.

In a particular embodiment, the chemotherapeutic agent is ananti-metabolite.

In particular embodiments, the chemotherapeutic agent is an antibioticor a plant derivative.

In a particular embodiment, the mammal is a human. In another particularembodiment, the mammal is a mouse.

In specific embodiments, the chemotherapeutic agent is administeredwithin 12 hours, 6 hours, 3 hours, 2 hours, or 1 hour of administeringthe IGF-1 receptor agonist. The chemotherapeutic agent can beadministered before, at the same time as, or after the IGF-1 receptoragonist. Preferably the chemotherapeutic agent is administered togetherwith (i.e., at approximately the same time as) or after the IGF-1receptor agonist. Where an agent is most active against cancer cells ina particular phase of the cell cycle, such as S phase, the IGF-1receptor agonist is preferably administered first. The chemotherapeuticagent is preferably administered later, after a time gap such that themaximum number of cells are in the phase of the cell cycle where theyare most sensitive when the chemotherapeutic agent is administered.

In specific embodiments, the cancer is lung cancer, prostate cancer,colorectal cancer, breast cancer, pancreatic cancer, leukemia, livercancer, stomach cancer, ovarian cancer, uterine cancer, testicularcancer, brain cancer, non-Hodgkin's lymphoma, Hodgkin's lymphoma,Ewing's sarcoma, osteosarcoma, neuroblastoma, rhabdomyosarcoma,melanoma, or brain cancer.

In particular embodiments, the IGF-1 receptor agonist is IGF-1 orcontains IGF-1.

In particular embodiments, the chemotherapeutic agent ismechlorethamine, cyclophosphamide, ifosfamide, melphalan, chlorambucil,thiotepa, hexamethylmelamine, busulfan, carmustine, lomustine,semustine, streptozocin, decarbazine, vincristine, vinblastine,etoposide, teniposide, paclitaxel, docetaxel, daunorubicin, idarubicin,doxorubicin, epirubicin, dactinomycin, plicamycin, mitomycin C,bleomycin, mitoxantrone, methotrexate, fluorouracil, floxuridine,fludarabine, mercaptopurine, thioguanine, cytarabine, azacytidine,cladribine, pentostatin, cisplatin, carboplatin, mitotane, procarbazine,or amsacrine.

In particular embodiments, the chemotherapeutic agent is methotrexate.In other embodiments, it is doxorubicin.

In a particular embodiment, the IGF-1 receptor agonist is not an insulinreceptor ligand.

In specific embodiments, the IGF-1 receptor agonist has a K_(D) for theinsulin receptor of greater than 0.5 nM, greater than 1 nM, or greaterthan 2 nM.

The invention also provides a method of inhibiting growth of cancercells comprising: contacting the cells with an anti-cancerchemotherapeutic agent and an IGF-1 receptor agonist; wherein the IGF-1receptor agonist is not insulin, and wherein the anti-cancerchemotherapeutic agent is not doxorubicin.

In particular embodiments of the method, the IGF-1 receptor agonist hasa binding affinity for the IGF-1 receptor greater than insulin.

In particular embodiments of the method, at least a portion of thecancer cells are killed.

The contacting can be in vitro or in vivo.

The invention also provides a method of treating cancer in a mammalinvolving administering to the mammal an anti-cancer chemotherapeuticagent and an IGF-1 receptor agonist, wherein the IGF-1 receptor agonistis not insulin.

In particular embodiments of that method, the chemotherapeutic agent isnot doxorubicin.

In the method involving administering a chemotherapeutic agent and anIGF-1 receptor agonist, the chemotherapeutic agent and agonist aretypically not physically associated. But they may be in some embodimentsnon-covalently associated, e.g., in nanoparticles.

In particular embodiments of the conjugate compounds and methods of theinvention, the insulin receptor ligand has a K_(D) for the insulinreceptor of less than 10 μM, less than 1 μM, less than 100 nM, less than50 nM, less than 20 nM, less than 10 nM, less than 5 nM, less than 2 nM,or less than 1 nM.

In particular embodiments of the conjugate compounds and methods of theinvention, the IGF-1 receptor ligand has a K_(D) for the IGF-1 receptorof less than less than 10 μM, less than 1 μM, less than 100 nM, lessthan 50 nM, less than 20 nM, less than 10 nM, less than 5 nM, less than2 nM, or less than 1 nM.

Guidelines for Coupling Anti-Cancer Chemotherapeutic Agents to ReceptorLigands

The natural ligands to the insulin and IGF-1 receptors are proteins,namely insulin, IGF-1, and IGF-2. Chemotherapeutic agents are typicallycoupled to proteins through the reactive groups present on proteins.These include the N-terminal alpha-amino group, the C-terminalalpha-carboxyl group, the side-chain amino group of lysine, theside-chain carboxyl groups of aspartic acid and glutamic acid, the sidechain thiol of cysteine, and the side chain of arginine. Other reactiveside chains found on proteins are the side-chain hydroxyl of serine andthreonine, the hydroxyaryl of tyro sine, the imidazole of histidine, andthe methionine side chain.

Many of the same reactive groups are found on chemotherapeutic agentsand on non-proteinaceous ligands of the insulin and IGF-1 receptors.Thus, many of the principles of modification and cross-linking ofproteins discussed herein also apply to modification and cross-linkingof chemotherapeutic agents and non-proteinaceous ligands.

The chemistry and principles of protein conjugation and cross-linkingare described in Wong, Shan S., Chemistry of Protein Conjugation andCross-Linking, 1991, CRC Press, Boca Raton, Fla. Other sources forinformation on this chemistry include the Pierce Biochemistry catalog;and Greene, T. W., and Wutz, P. G. M., Protecting Groups in OrganicSynthesis, second edition 1991, John Wiley & Sons, Inc., New York, andreferences cited therein.

The strongest nucleophile of amino acid side chains is the thiol ofreduced cysteine side chains. The thiol reacts with most proteinmodifying reagents. Alpha-haloacetamides and maleimides are consideredto react specifically with cysteine residues, particularly at pH 7.0 andbelow. Thiols also react by disulfide interchange with disulfidereagents.

Amino groups are the next-strongest nucleophiles found on proteins.Aldehydes react with amino groups to form Schiff bases. The Schiff basesare hydrolyzable, which can be an advantage in the present invention.With uptake into cancer cells of a ligand-chemotherapeutic agentconjugate, in some cases it is necessary that the chemotherapeutic agentis cleaved from the conjugate for it to be active. This is betteraccomplished if the chemotherapeutic agent is linked to the ligand by acleavable linkage, such as a hydrolyzable linkage. Cleavable linkagescan be cleaved spontaneously or by enzymes in the cell. For instance,amide bonds are cleaved by certain enzymes, including proteases. ASchiff base linkage spontaneously hydrolyzes at an appreciable rate. Adisulfide linkage is expected to be reductively cleaved in theintracellular reducing environment of a cancer cell.

The Schiff base formed by reaction of an amino group with an aldehydecan be stabilized by reduction with, for instance, sodium borohydride orpyridine borane. Pyridine borane has the advantage of not reducingdisulfides, which are found in insulin, IGF-1, and IGF-2 and areessential for the structure of those proteins.

Sugars or other moieties having hydroxyl groups on adjacent carbons,which are found in some chemotherapeutic agents, can be modified toreact with amino groups by oxidizing the sugars with, for instance,periodate. This cleaves between the carbons and produces a dialdehyde.The aldehyde groups will react with amino groups.

A dialdehyde, such as glutaraldehyde, will cross-link two moleculeshaving amino groups.

Other amino reagents include activated carbonyls, such asN-hydroxysuccinimide esters, p-nitrophenyl esters, or acid anhydrides(e.g., succinic anhydride).

Amino groups also react with sulfonyl halides and aryl halides (e.g,2,4-dinitrofluorobenzene).

Amino groups also react with isocyanates and isothiocyanates to formurea or thiourea derivatives.

Imidoesters are the most specific acylating agents for amino groups.Imidoesters react specifically with amines to from imidoamides at pHsbetween about 7 and 10. This reaction has the advantage of maintainingcharge stability by generating a positively charged group, theimidoamide, at the former amino group. Imidoamides also slowly hydrolyzeat pHs above neutrality, which can also be an advantage in that thehydrolysis can release free chemotherapeutic agent in the cancer cell.

Carboxyl groups react specifically with diazoacetate and diazoacetamideunder mild acid conditions, e.g., pH 5.

The most important chemical modification of carboxyls usescarbodiimides, such as1-cyclohexyl-3-(2-morpholinyl-4-ethyl)carbodiimide (CMC) and3-(3-dimethylaminopropyl)carbodiimide (EDC). In the presence of anamine, carbodiimides form an amide bond to the carboxyl in two steps. Inthe first step, the carboxyl group adds to the carbodiimide to form anO-acylisourea intermediate. Subsequent reaction with an amine yields thecorresponding amide.

A particularly important carbodiimide reaction is its use in activatingcarboxyls with N-hydroxysuccinimide to form an N-hydroxysuccinimideester.

The activated carboxyl is stable enough to be isolated, but will thenreadily react with amino groups to form an amide bond.

Succinimides such as N-succinimidyl-3-[2-pyridyldithio]propionate (SPDP)can be used to couple two compounds through amino groups. (See PierceBiotechnology catalog, and Thorpe, P. E. et al. 1982, Immunol. Rev.62:119-158.)

Arginine reacts with vicinal dialdehydes or diketones, such as glyoxal,2,3-butanedione, and 1,2-cyclohexanedione. Borate may stabilize theadduct, if stabilization is desired.

The reactive groups can also be interchanged with other reactive groupsby some of the above reactions. For instance, modification of an aminogroup with an acid anhydride such as succinic anhydride, replaces thepositively charged amino group with a free carboxyl group. Likewise,reaction of a carboxyl group with a carbodiimide and a diamine, such asethylene diamine, replaces the carboxyl group with a free amino group.

Cross-linking: Reagents containing two of the reactive groups describedabove, for instance two amino-reactive groups or an amino-reactive and athiol-reactive group, can be used to cross-link a chemotherapeutic agentcontaining one of the appropriate groups to an insulin or IGF-1 receptorligand containing the other appropriate group. In addition, a carboxyl(of, e.g., a chemotherapeutic agent) activated with a carbodiimide or acarbodiimide and N-hydroxysuccinimide can react with an amino group (of,e.g., a protein ligand) to form an amide bond cross-link.

Insulin, IGF-1, and IGF-2

The structure of human insulin is shown below.

The sequence of human insulin-like growth factor-1 (IGF-1) is shownbelow as SEQ ID NO:1.

(SEQ ID NO: 1) GPETLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSA

The amino acid sequence of human IGF-2 is shown below as SEQ ID NO:2.

(SEQ ID NO: 2) AYRPSETLCGGELVDTLQFVCGDRGFYFSRPASRVSRRSRGIVEECCFRSCDLALLETYCATPAKSE

The cysteine residues in all three proteins are all in disulfidebridges. Thus, the most nucleophilic free side chains present on theproteins are the lysine amino groups, of which there is one in insulin,three in IGF-1, and one in IGF-2. In addition insulin has two peptidesand thus two N-terminal alpha-amino groups, while IGF-1 and IGF-2 haveone N-terminal alpha-amino group each. Other reactive side-chains,including carboxyl-containing side chains, histidine side chains, andarginine side chains, are also present on the proteins, as well as theC-terminal alpha-carboxyl groups.

A preferred IGF-1 variant with reduced binding affinity for the solubleIGF-1 binding proteins is LONG-R3-IGF-1 (GroPep Ltd., Australia), whichhas the sequence

(SEQ ID NO: 4) MFPAMPLSSL FVNGPRTLC GAELVDALQF VCGDRGFYFN KPTGYGSSSRRAPQTGIVDEC CFRSCDLRRL EMYCAPLKPA KSA

The invention will now be illustrated by the following examples. Theexamples are intended to illustrate the invention but not to limit thescope of the invention.

EXAMPLES Synthetic Example 1 Methotrexate Coupling to Insulin, IGF-1,and IGF-2

Two-step procedure: This procedure is modified from Stehle, G., et al.,Anti-Cancer Drugs 8:677 (1997) and Bures, L., et al., Neoplasma 35:329(1988). Methotrexate (MTX) is dissolved in water at 20 mg/ml. An NaOHsolution can be added dropwise to assist dissolving the MTX free acid.To 1 ml of this MTX solution, 14 mg N,N′-dicyclohexylcarbodiimide (DCC)and 50 mg of N-hydroxysuccinimide are added. The mixture is incubatedfor 12 hours to form activated MTX, methotrexate-succinimide ester(MTX-SE) (Scheme 1).

If desired, activated MTX-SE can be separated from MTX by thin-layerchromatography, as described in Stehle, G., et al., Anti-Cancer Drugs8:677 (1997). MTX-SE is slowly added to a solution of 5-10 mg/ml insulinin 0.13 M sodium phosphate, pH 7.4. To achieve a loading rate of about 1mole MTX per mole insulin, approximately 10 mg of MTX-SE is added per100 mg of insulin. After coupling, the coupled MTX-insulin is separatedfrom unreacted MTX and MTX-SE by separation with SEPHADEX G-25 or G-10chromatography. This procedure couples MTX predominantly to free primaryamine groups. Insulin has three primary amines—one lysine residue with aside chain amine, and two peptides, each with a N-terminal alpha-aminogroup.

The amount of unbound MTX in the low molecular weight fractions from theSEPHADEX G-25 or G-10 chromatography can be determined by absorption at370 nm in sodium bicarbonate buffer, 0.17 M, pH 8.5. By subtraction fromthe amount of starting MTX-SE added to insulin, the amount of coupledMTX can be calculated.

If desired, the different species of insulin resulting from the couplingcan be separated by ion-exchange or hydrophobic exchange FPLC(Pharmacia, Inc.), reverse-phase HPLC, or other techniques known topersons of skill in the art. The different species include unreactedinsulin, the species of insulin with one MTX coupled through itsterminal carboxyl to one of the three amino groups on insulin, speciesof insulin with two MTX coupled through their terminal carboxyls to twoof the amino groups, and the one species with an MTX coupled through itsterminal carboxyl to each of the three amino groups. The three speciesof insulin with one MTX coupled through its terminal COOH to an aminogroup of insulin, are shown below.

In addition, the MTX-insulin species will include species with MTXcoupled through its other carboxyl group to the amino groups of insulin.

One-step procedure: Insulin (100 mg) is dissolved in water (50 ml) andthe pH adjusted to 7.2. Ten to fifty mg MTX (free acid) is dissolved in40 ml water with dropwise addition of a NaOH solution, and the pHadjusted to 7.2. The insulin and MTX solutions are mixed, solid1-ethyl-3-(3′-dimethylaminopropyl)-carbodiimide methoiodide (EDC) (480mg) is added, and the solution is stirred for 20 hours. The pH ismonitored and maintained at 7.2-7.5 by addition of 0.5 M HCl. Afterreaction, the mixture is concentrated by ultrafiltration or othermethods known to persons of skill in the art, such as lyophilization,water absorption by SEPHADEX G-10, or dialysis against solid sucrose.The concentrated insulin-MTX solution is passed through a SEPHADEX G-10column to remove unreacted MTX and EDC.

The one-step procedure produces some cross-linking of insulin-MTXmonomers by EDC cross-linking of the carboxyl groups of the insulin orMTX of one insulin-MTX monomer with an amino group of the insulin or MTXof another MTX monomer. Insulin-MTX prepared by the two step procedurewill not be polymerized, but polymers could be prepared by reacting theinsulin-MTX monomers with EDC or DCC. There may be some advantage topolymerizing insulin-MTX because the polymers may bind more tightly tothe insulin and IGF-1 receptors.

If it is found that the amino groups of insulin are essential tobinding, other reactive groups can be used for coupling. For instance,carboxyl side chains or the C-termini carboxyl groups can be activatedwith carbodiimide or a carbodiimide and an N-hydroxysuccinimide. Thecarboxyls of methotrexate can be modified with a carbodiimide andethylene diamine to append a reactive amino group to MTX. The free aminogroup of the appended ethylene diamine moiety can then react with theactivated carboxyl of insulin to couple MTX to insulin.

Other methods of coupling MTX to insulin will be apparent to persons ofskill in the art.

Methotrexate can be coupled to IGF-1 or IGF-2 by the procedures used tocouple methotrexate to insulin.

Synthetic Example 2 Doxorubicin Coupling to Insulin, IGF-1, and IGF-2

The structure of doxorubicin is shown below.

The most reactive group on doxorubicin for coupling is the amino group.

Doxorubicin can be coupled through its amino group to an amino group oninsulin by reaction with a di-imidoester, such asdimethyladipimidate-2-HCl (Pierce Biochemical, Inc.), or adisuccinimidyl ester, such as disuccinimidyl glutarate (PierceBiochemical, Inc.). One of the products generated by coupling withdimethyladipimidate is shown below.

Coupling also occurs with the two terminal alpha-amino groups ofinsulin.

A solution containing insulin at approximately 3 mg/ml (0.5 mM) and 5 mMdoxorubicin is prepared in carbonate buffer, pH 8.8. DMA is added to 5mM concentration and the solution incubated at room temperature or 37°C. for 15 minutes to 1 hour. The reaction is quenched by the addition ofexcess Tris buffer. Protein is separated from buffer and unreactedreagents by SEPHADEX G-10 chromatography.

Synthetic Example 3 5-Fluorouracil Coupling to Insulin, IGF-1, and IGF-2

Fluorouracil is coupled to a sugar or deoxysugar, such as2′-deoxyribose, to form a nucleoside. The sugar portion of thenucleoside is coupled to insulin, IGF-1, and IGF-2. In one embodiment,the starting material is deoxyuridine. Deoxyuridine is fluoridated toform 5-fluorodeoxyuridine. (Robins, M. J., 1976, J. Am. Chem. Soc.98:7381.)

First, the sugar hydroxyls of deoxyuridine are acetylated. To 12 ml ofAc₂O, is added 1.03 g 2′-deoxyuridine and 25 mg of4-N,N-dimethylpyridine. The mixture is allowed to react for 24 hours atroom temperature. The solution is then evaporated at 35° C. The residueis coevaporated with three 25 ml portions of ethanol.

Next, the acetylated deoxyuridine is fluoridated at the 5 position. Thesolid product of the previous step (0.624 g) is dissolved in 15 ml ofCHCl₃. CF₃OF (0.9 g) is dissolved in 10 ml of CCl₃F at −78° C. The CF₃OFsolution is added slowly to the deoxyuridine solution with stirring at−78° C., and the reaction is monitored by following the disappearance ofuracil absorption at 260 nm. After minimization of the 260 nmabsorption, stirring is continued for 5 minutes. Nitrogen gas is bubbledthrough the solution to remove excess CF₃° F. The solution is thenwarmed to room temperature and the solvents evaporated under reducedpressure.

To deacetylate the acetylated fluorodeoxyuridine, the residue of theprevious step is stirred in 50 ml MeOH with 6 ml of DOWEX 50-X8(H⁺)resin and filtered. The resin is washed thoroughly with MeOH and thewashes recovered. The methanol solvent is evaporated. The residue iscoevaporated with EtOH-EtOAc-PhCH₃ (1:1:2). The product is crystallizedfrom 20 ml of absolute ethanol.

The product is reacted with a difunctional cross-linker that activatesthe sugar hydroxyls, primarily the 5′ hydroxyl. In one embodiment,fluorodeoxyuridine is reacted with compound 11 in an anhydrous solventsuch as chloroform.

This adds compound 11 by the phosphate group to the 5′ hydroxyl,resulting in methoxyimidopropyl-FdUMP. (Some reaction with the 3′hydroxyl will also occur.) The imidoester group is then used tocross-link the compound to a protein amino group in aqueous medium toproduce the product shown below.

In another embodiment, the fluorodeoxyuridine is activated at elevatedpH with a bifunctional cross-linking agent such as disuccinimidylsuberate (DSS) and the activated fluorodeoxyuridine is reacted with aprotein to cross-link to an amino group on the protein. DSS (0.5 mMfinal concentration) is mixed in carbonate buffer at pH 10 withfluorodeoxyuridine (0.5 mM) and reacted for 1 hour at 4° C. The pH isadjusted to about 7-8 in phosphate or HEPES buffer. Insulin, IGF-1, orIGF-2 is added at approximately 0.5 mM and the reaction continued for 30min. The reaction is quenched by the addition of Tris buffer. Theprotein is concentrated by ultafiltration and then separated from saltsand unreacted reagents by SEPHADEX G-10 chromatography.

Synthetic Example 4 Bleomycin Coupling to Insulin, IGF-1, and IGF-2

The bleomycins have two free primary amino groups and a secondary amineavailable for coupling to amino groups of insulin, IGF-1, and IGF-2 withcross-linkers such as disuccinimidyl suberate or dimethyladipimidate.

Synthetic Example 5 Vincristine Coupling to Insulin, IGF-1, and IGF-2

Vincristine has one secondary amine available for coupling, and thus canbe coupled by bifunctional amine-reactive reagents, such as DSS or DMAto an amino group on insulin, IGF-1, or IGF-2.

Synthetic Example 6 Paclitaxel Coupling to Insulin, IGF-1, and IGF-2

Paclitaxel has no free reactive amino groups and no sulfhydryls, but hastwo available hydroxyls. The hydroxyls can be activated at elevated pHwith a bifunctional coupling agent such as DSS, and the activatedpaclitaxel can then be reacted with insulin, IGF-1, or IGF-2, resultingin coupling to an amino group on the protein.

Synthetic Example 7 Etoposide Coupling to Insulin, IGF-1, and IGF-2

The phenolic hydroxyl of etoposide will nucleophilically attack aphosphoryl halide to form etoposide phosphate. (U.S. Pat. No.5,041,424.) An analogous reaction can be used to couple etoposide toinsulin, IGF-1, or IGF-2.

Etoposide is dissolved in dry acetonitrile. A bifunctional reagentcontaining a phosphoryl halide at one end and an amine-reactive agent atthe other, such as compound 12 below, is added to react with etoposide.The activated etoposide product is purified and then mixed with protein,where the second functionality of the cross-linker reacts with an aminegroup of the protein to cross-link etoposide phosphate to the protein.

Alternatively, in a one step procedure, etoposide and protein can bemixed together with a cross-linker such as DMA or DSS. The phenolichydroxyl of etoposide and an amino group of the protein will react withthe two functionalities of the cross-linker to cross-link etoposide andthe protein together, as is described for doxorubicin and fluorouracilcoupling.

Synthetic Example 8 Cyclophosphamide Coupling to Insulin, IGF-1, andIGF-2

Cyclophosphamide has the structure shown below. It is oxidized inmammals in vivo and decomposes to the active species phophoramidemustard. (Kwon, C.-H., et al., 1991, J. Med. Chem. 34:588.)

Cyclophosphamide can be coupled, for instance, through a ribose andpyrimidine to an amino group in insulin, IGF-1, or IGF-2. The structurebelow, bischloroethylphosphoramide-thymidine-amine (BCPTA) issynthesized, and then cross-linked through its free primary amino groupto the protein.

To prepare BCPTA, 5′-amino-2′-deoxy-aminocytidine (13) is synthesized byknown chemical procedures.

A solution of bis(2-chloroethyl)phosphoramidic dichloride (2 mmol) in 5ml ethyl acetate is added to a stirred mixture of5′-amino-2′-deoxy-aminocytidine (13) (2 mmol) and triethylamidine (4mmol) in 15 ml dimethylformamide and stirred at room temperature for 48hours. (Lin, T.-S., et al., 1980, J. Med. Chem. 23:1235.) Afterisolation of the product bischloroethylphosphoramide-thymidine-amine,the product is cross-linked to amino groups of insulin, IGF-1, or IGF-2by a difunctional cross-linker such as DMA or DSS as described insynthetic examples 2 and 3.

Example 1 Synthesis and in vitro Testing of Three Methotrexate-InsulinConjugates

Three insulin-MTX conjugates were synthesized by the one-step procedureof synthetic example 1.

Conjugate Insulin-MTX-A. This conjugate was designed to haveapproximately 3 MTX attached to each insulin by direct amide bonds tothe two alpha amino groups and one lysine side chain of insulin. MTX(20.1 mg) was dissolved in 0.5 ml 20 mM sodium phosphate, pH 7.4, and 77μl 1M NaOH (NaOH added to neutralize and dissolve the MTX). Insulin (9.1mg) was dissolved in 0.5 ml 20 mM sodium phosphate, pH 7.4. The insulinand MTX solutions were mixed. EDC (27.3 mg) was dissolved in 20 mMsodium phosphate pH 7.4 and immediately added to the insulin-MTXsolution to give a final volume of 1.2 ml. The reaction was allowed toproceed at room temperature for 2 hours. The product mixture was passedthrough a 10 ml PD-10 column equilibrated with 30 mM glycine-NaOH, pH10.5, to separate the insulin-MTX conjugate from unreacted MTX and otherreagents on the basis of size. The product was analyzed by opticalspectroscopy in pH 7.4 buffer to measure the absorbance at 372 nm toquantify methotrexate. Assuming 100% recovery of insulin, and usingε_(372 nm)=6.85 mM⁻¹, the molar ratio of methotrexate to insulin was3.4.

Conjugate Insulin-MTX-B. This involved a conjugate of methotrexatethrough a peptide linker to insulin. First, methotrexate was conjugatedthrough its terminal carboxyl group to the amino terminus of thetetrapeptide (Ala-Leu-Ala-Leu, SEQ ID NO:5). Peptide (1.8 mg) and MTX(4.6 mg) (a 1:1 molar ratio) were dissolved together in 25 mM sodiumphosphate, pH 7.4, in a final volume of 0.5 ml. Solid EDC (4 mg) wasadded to the solution, and the reaction proceeded for 2 hours at roomtemperature. A small aliquot of the product was analyzed by thin-layerchromatography on silica plates with 50% acetone, 50% methanol as themobile phase. The MTX-peptide reaction product migrated slower thanunreacted MTX, indicating that the conjugation was successful.

The MTX-peptide product mixture was added to 4.51 mg insulin in a finalvolume of 0.74 ml 25 mM sodium phosphate pH 7.4. (This has apeptide:insulin molar ratio of 6:1.) EDC (13 mg freshly dissolved inwater) was added to the mixture to give a final volume of 0.83 ml. Thereaction was allowed to proceed at room temperature for 2 hours. Theproduct mixture was passed through a 10 ml PD-10 column to separateinsulin-conjugate product from unreacted smaller reagents. Opticalspectroscopy indicated the product has approximately 3 MTX per insulin.

Conjugate Insulin-MTX-C. This conjugate was a conjugate with MTXdirectly attached to insulin without a linker as in the insulin-MXT-Aconjugate, but with only approximately 1 MTX per insulin. Insulin (11.8mg) and MTX (1.38 mg) (a molar ratio of MTX:insulin of 1.5:1) weredissolved and mixed as described for the synthesis of conjugateInsulin-MTX-A. Freshly dissolved EDC (18 mg) was added to the mixtureand the reaction was allowed to proceed at room temperature for 2 hours.The product was found to form a precipitate, which could be dissolved byadding glycine-NaOH buffer (50 mM glycine) and adjusting the pH to 10.5with NaOH. The solubilized product mixture was passed through a 10 mlPD-10 column to separate the conjugate from unreacted reagents on thebasis of size. The purified insulin-MTX conjugate was determined to haveapproximately 1.0 MTX per insulin by the absorbance at 372 nm.

The three types of conjugates were analyzed by SDS-PAGE. In addition toconjugating methotrexate to insulin, the conjugation procedure cancouple insulin molecules together through an amino group of one insulinto a carboxyl group of another to form dimers, trimers, or highermultimers. The multimers may also have methotrexates attached to them.The SDS-PAGE analysis of conjugate insulin-MTX-A is shown in FIG. 1. Themajority of product was monomer with some dimer and trimer. Very similarresults were found for the conjugates insulin-MTX-B and insulin-MTX-C.

In vitro growth inhibition. The mouse fibrosarcoma cell line FSAII wascultured in RPMI medium supplemented with 10% fetal calf serum (FCS)(rich medium). The cells were grown in a 5% CO₂ atmosphere at 37° C. in100 cm² plastic tissue culture dishes (20 ml medium). Cells were passedevery 4-6 days and seeded at 2×10⁶ cells per plate. Cells were harvestedby washing once in Hank's balanced salt solution, and then digestingwith 3 ml of trypsin-EDTA for 3-10 minutes until cells had detached.Trypsinization was stopped by adding rich medium. The harvested cellswere washed by centrifugation and resuspended in rich medium, and thenplated in a 96-well plate at 12,000 cells per well in rich medium.Plates were incubated in the rich medium 16 hours and then transferredto minimal medium (100 μl/well), which lacked serum and thus lackedinsulin and IGF and other growth factors. Minimal medium was RPMIsupplemented with 10 μg/ml transferrin (iron-loaded) and 200 μg/mlbovine serum albumin. The cells were adapted to minimal medium for 6hours, and then methotrexate or a test methotrexate conjugate was addedat concentrations from 2 nM to 2 μM (methotrexate or methotrexate groupsin the conjugates). Each condition was tested in triplicate. After 72hours incubation at 37° C., cell proliferation was assayed by thecell-counting kit-8, based on tetrazolium dye reduction, similar to theMTT assay (Dojindo Molecular Technologies, Gaithersburg, Md.). Theresults are shown in FIG. 2.

Methotrexate and all three conjugates inhibited FSAII proliferation. Theminimum inhibitory concentration of the conjugates to inhibitproliferation was similar to or slightly higher than unconjugatedmethotrexate. There were no significant differences between minimuminhibitory concentrations of the three types of insulin-methotrexateconjugates.

The conjugates and methotrexate were also tested against other malignantcell lines including the human breast line MCF-7, the human prostatecancer line LNCAP, and the mouse mammary cancer line SCK. The resultswere very similar to those shown for FSAII (data not shown). Inhibitionwas also tested in rich medium, and the results were similar to thoseobtained in minimal medium (data not shown).

These results show that the insulin-MTX conjugates tested all were ableto enter malignant cells and exert cytotoxic effect similar tomethotrexate. This indicates the methotrexate portion of the conjugateis cleaved from the conjugate or is able to exert its cytotoxic effectwhile bound to the conjugate.

Example 2 Insulin and IGF Receptor Number and Cell ProliferationResponse to Insulin and IGF-1

We analyzed several cancer cell lines for expression of IGF-1 receptorsand insulin receptors on the cell surface. The cell lines tested wereLNCAP (human prostate carcinoma), MCF-7 (human breast carcinoma),MDA-231 (human breast carcinoma), SCK (mouse mammary carcinoma), FSAII(mouse fibrosarcoma), and HOP-92 (human lung adenocarcinoma). Cells werecontacted with fluorescently labeled antibodies recognizing the insulinand IGF-1 receptors and analyzed by flow cytometry, also known asFluoresence Activated Cell Sorting (FACS).

The results are shown in FIG. 3. The fluorescence value of the fixedcells not treated with the insulin or IGF receptor antibodies is fixedat 1. A fold increase of fluorescence of greater than 1 in the insulinor IGF bars indicates the presence of insulin or IGF receptors, and therelative abundance of the receptors can be compared between differentcell lines. The results show all the cell lines had some insulin andIGF-1 receptors. IGF-1 receptors were more abundant than insulinreceptors in all cell types. The two mouse cell lines SCK and FSAIIappeared to have lower levels of insulin and IGF receptors than thehuman cell lines, but this could be an artifact from the fact that theantibodies used were antibodies against the human receptors.

The cell lines LNCAP, MCF-7, MDA-231, SCK, and HOP-92 were also testedto determine whether the cells increased their proliferation in thepresence of insulin or IGF-1. Cells were plated in minimal medium withno addition (negative control), 1 ug/ml insulin, 100 ng/ml IGF-1, or 10%fetal calf serum (positive control), and cell density was monitored at1, 2, and 4 days after plating. The data showed that both insulin andIGF-1 stimulated proliferation of all the cell lines except HOP-92.(Data not shown).

Example 3 In vivo Testing of a Methotrexate-Insulin Conjugate

The conjugate insulin-methotrexate-A, having approximately 3methotrexate per insulin attached by direct amide bonds to amino groupson insulin was synthesized by the following procedure. Insulin (480 mg)was dissolved in 6 M urea, 25 mM sodium phosphate pH 7.4. Methotrexate(280 mg) was dissolved in the same buffer (with sodium hydroxide addedto neutralize the acidic methotrexate and bring the pH up to 7.4) andmixed with the insulin in a final volume of 25 ml. Solid EDC (1.4 g) wasadded and the reaction was allowed to proceed at room temperature for 2hours. After the reaction, a precipitate was formed which wassolubilized by addition of glycine and NaOH to 50 mM glycine and pH10.5. The product was passed 16 ml at a time through a 70 ml SEPHADEXG-25 column equilibrated with 50 mM glycine-NaOH, pH 10.5, to separatethe conjugate product from unreacted methotrexate, urea, and otherreagents. The purified product was found to contain 2.72 MTX per insulinby the absorbance at 372 nm. The product was mixed with glycerol to 10%w/v glycerol before freezing for storage.

FSAII testing. Six-week old female mice were injected subcutaneously inthe thigh with 200,000 FSAII cells each in serum-free medium. Tumorswere allowed to grow until they reached an average volume of 100 mm³(calculated as length×breadth²). At that time, treatment was initiated.Mice were injected intraperitoneally with 60 μmoles/kg (high dose) or 15μmoles/kg (low dose) methotrexate in the form of unconjugatedmethotrexate or insulin-methotrexate-A conjugate. A fifth group of micewas untreated controls. Each group contained five mice. Mice weretreated on days 0, 2, and 5. Tumor growth was measured every second day.The results are shown in FIG. 4.

Neither the high or low dose of methotrexate had any apparent effect ontumor growth. The low dose of the insulin-methotrexate conjugatesignificantly slowed tumor growth as compared to untreated controls. Thehigh dose of the insulin-methotrexate conjugate appeared to verysignificantly slow tumor growth but was more toxic. It killed all fivemice by one day following the third treatment.

Thus, the low dose of the conjugate was more effective than the highdose of unconjugated methotrexate. The conjugate was at least 4-foldmore active against the FSAII tumors in vivo than unconjugatedmethotrexate.

LNCAP testing. Eight-week old athymic male mice (nu/nu) were injectedsubcutaneously in the thigh with 1 million LNCAP cells in serum-freemedium. Tumors were allowed to grow until they reached an average sizeof 100 mm³. Mice were then treated on days 0, 4, and 8, and again ondays 18, 22, and 26 with 40 μmoles/kg (high dose) or 15 μmoles/kg (lowdose) methotrexate in the form of unconjugated methotrexate orinsulin-methotrexate-A conjugate. A fifth group of mice was untreatedcontrols. The results are shown in FIG. 5.

The results were similar to the results with FSA. The low doseinsulin-methotrexate conjugate appeared to slow tumor growth, while thehigh and low dose unconjugated methotrexate appeared to have no effect.The high dose insulin-methotrexate conjugate was toxic despite theslightly lower dose and greater time between doses that was used in thisexperiment as compared to the FSAII experiment.

Conclusions: The insulin-methotrexate conjugate was effective at atleast 4-fold lower concentration than unconjugated methotrexate againstFSAII tumors in mice and at at least 2.6 times lower concentration thanunconjugated methotrexate against LNCAP tumors in mice.

Example 4 Synthesis of an IGF-Methotrexate Conjugate

This conjugate was a conjugate of methotrexate to a variant of IGF-1called LONG-R3-IGF-1 (GroPep, Ltd., Australia). LONG-R3-IGF has thefirst 11 residues of methionyl porcine growth hormone followed byVal-Asn and the human IGF-1 sequence with and Arg substituted atposition 3 of the IGF-1 sequence. Its sequence is SEQ ID NO:4.LONG-R3-IGF-1 has reduced binding affinity for soluble IGF bindingproteins but equal binding affinity for the type 1 IGF receptor andequal or greater biological activity as compared to wild-type IGF-1(Francis, G. L., et al.1992, J. Mol. Endocrinol. 8:213-223; Tomas, F. M.et al., 1993, J. Endocrinol. 137:413-421).

LONG-R3-IGF-1 (1.5 mg) was dissolved in 0.3 ml of 10 mM HCl. It wasdialyzed against 25 mM sodium phosphate, 10 mM NaCl, 6.3 M urea, pH 7.4,overnight. Then 84 μl MTX in the same buffer was added to the sample inthe dialysis bag (3,000 m.w. cutoff). Then 15 mg EDC freshly dissolvedin the same buffer was added. The sample in the dialysis bag was placedin a dish in air to react for 2 hours at room temperature. Then the bagwas placed again in the same dialysis buffer and dialyzed overnight toremove unreacted methotrexate and other reagents. Then the sample wasdialyzed for 12 hours against 25 mM sodium phosphate, pH 7.4. Theproduct precipitated following this dialysis. Next, the dialysis bag wasplaced in 10 mM HCl, which solubilized the product. Optical absorbanceat 372 nm of the sample was determined diluted into pH 7.4 buffer toquantify methotrexate in the conjugate. The conjugate was determined tocontain 2.94 MTX per LONG-R3-IGF-1 by this method, using ε_(372 nm)=6.85mM⁻¹ for methotrexate.

Example 5 In vitro Cytotoxic Activity of the Methotrexate-IGF-1Conjugate

The IGF-methotrexate conjugate of Example 5 was tested for inhibition oftumor cell proliferation in vitro against LNCAP cells. LNCAP cells wereplated in a 96-well plate at 3,000 cells per well in RPMI mediumsupplemented with 10% fetal bovine serum (FBS). After incubationovernight, the medium in the wells was replaced with 100 μl per well ofRPMI supplemented with 0.1% FBS. The conjugate and unconjugatedmethotrexate were added to the wells in triplicate at concentrationsranging from 2 nM to 2 μM. After incubation for 4 days, cellproliferation was assayed with the cell counting kit-8 (DojindoMolecular Technologies, Gaithersburg, Md.). The results are shown inFIG. 6. The IGF-MTX conjugate and unconjugated methotrexate bothinhibited growth with a minimum inhibitory concentration ofapproximately 500 nM to 2 μM. Similar results were obtained withproliferation assays in rich medium containing 10% FBS (Table 1).

The data of Table 1 also show that the minimal inhibitory concentrationof unconjugated methotrexate in minimal medium containing 0.1% serum wasabout 2000 nM, whereas in rich medium containing 10% serum it was about125 nM. Thus, serum, with its growth factors including IGF-1 andinsulin, substantially decreased the concentration of methotrexateneeded to inhibit growth of LNCAP tumor cells.

TABLE 1 LNCAP proliferation in vitro. Cell number (relative units) MTXIGF-MTX MTX IGF-MTX conc. MTX conjugate Minimal conjugate (nM) Richmedium Rich medium med. Minimal med. 2000 0.147 ± .005 0.234 ± .0040.418 ± .026  .255 ± .014 500 0.163 ± .009 0.381 ± .008 .706 ± .051 .635± .038 125 0.223 ± .012 0.891 ± .017 .835 ± .048 .921 ± .014 32 1.017 ±.033 1.248 ± .018 .994 ± .226 .921 ± .014 8 0.596 ± .071 0.674 ± .036.737 ± .043 .794 ± .028 2 0.724 ± .015 0.716 ± .021 .653 ± .046 .677 ±.057

Example 6 Methotrexate Activity in Human Breast Cancer Model, whereMethotrexate is Coupled to Insulin, IGF-1, or IGF-2, or Coadministeredwith Insulin or IGF-1

In vitro Testing:

MCF-7 is a human breast cancer cell line that is responsive to bothinsulin and IGF-1 (Alabaster, O., et al., 1981, Eur J Cancer Clin.Oncol. 17: 1223-1228; Dupont, J., et al., 2003, J. Biol. Chem.278:37256).

MCF-7 cells are cultured in F12/DME medium supplemented with 5% fetalcalf serum (FCS) in 95% air, 5% CO₂ at 37° C. (Karey, K. P. et al.,1988, Cancer Res. 48:4083-4092.) Cells are transferred every 4-6 daysand seeded at 1.75×10⁶ cells/plate in 20 ml medium in a 10 cm dish. Forthe assays, the cells were washed with sterile saline, detached from theplate in 3 ml of trypsin-EDTA in Hank's buffered salt solution. Aftercells are detached from the plate (2-4 minutes at room temperature), thetrypsin is inactivated by the addition of 4 ml of PBS containing 0.1%soybean trypsin inhibitor. The cells are then washed three times inTf/BSA (F12/DME supplemented with 10 μg/ml transferrin and 200 μg/mlbovine serum albumin). Cells are seeded at 1,000-20,000 cells in 2 ml ofTf/BSA medium in 35 mm diameter culture plates. Twenty-four hours afterplating, the cells are treated with MTX (10⁻¹⁰-10⁻³ M), MTX and insulin,MTX and IGF-1, at a range of methotrexate concentrations. Theconcentration of unconjugated IGF-1 is 50 ng/ml when present. Theconcentration of unconjugated insulin is 1 μg/ml when present. Controlstreated with no agent, insulin, or IGF-1 or with 5% FCS are alsoconducted.

Total cells are counted by microscopy and live cell number is determinedby Trypan blue staining on the 7th day of culture (after 6 days ofexposure to MTX or the other agents).

The IC₅₀ of MTX for inhibition of cell growth is determined under eachof the tested conditions. It is determined that when administered withinsulin or IGF-1, lower concentrations of MTX are needed to achieve thesame extent of inhibition of cell growth.

In vivo Testing:

MCF-7 cells are cultured as described above. Six-week-old female nudemice (nu/nu, Sprague Dawley, Madison, Wis.) are injected subcutaneouslyin the back with 5×10⁶ MCF-7 cells in 0.05 ml serum-free medium.Estrogen production in the mice is inadequate to support growth ofMCF-7, so the mice are given injections of beta-estradiol dissolved insesame oil (0.1 mg/0.05 ml oil s.c.) beginning one day before injectionof the cancer cells and weekly thereafter. Tumors are allowed to growuntil a diameter of 5 mm. (Hardman, W. E., et al., 1999, Anticancer Res.19:2269.)

When tumors reach a diameter of 5 mm, mice are treated once daily withMTX over a range of concentrations, or the mice are treated with insulinor IGF-1, and then 30 minutes later with MTX over a range ofconcentrations. The mice are fasted for 4 hours prior to treatment, andare given access to food immediately after treatment. Tumor size ismeasured by calipers twice weekly.

It is found that equal or better tumor shrinkage is achieved with lowerdoses of methotrexate when the methotrexate is administered inconjunction with insulin or IGF-1. This allows the same or betterkilling of tumors with lower side effects.

Example 7 Doxorubicin Activity in Human Colon Cancer Model, whereDoxorubicin is Coupled to Insulin, IGF-1, or IGF-2, or Coadministeredwith Insulin or IGF-1

In vitro Testing:

HT29 is a human colorectal cancer cell line that is responsive toinsulin and IGF-1 (Riera, L., et al., 2002, Biochim. Biophys. Acta1589:89; Valee, S., et al., 2003, Biochem. Biophys. Res. Commun.305:831).

Doxorubicin-insulin, doxorubicin-IGF-1, and doxorubicin-IGF-2 conjugateswith approximately one doxorubicin per protein molecule are prepared asdescribed in Synthetic Example 2.

HT29 cells are grown in RPMI 1640 medium supplemented with 10% fetalcalf serum. Confluent cells are trypsinized, washed, and cultured inTf/BSA (minimal medium) as described in Example 6. After 1 day ofadaptation to the minimal medium, doxorubicin, doxorubicin and insulin,doxorubicin and IGF-1, the doxorubicin-insulin conjugate, thedoxorubicin-IGF-1 conjugate, or the doxorubicin-IGF-2 conjugate at arange of concentrations is added to each plate. Doxorubicin, forinstance, is at a range of about 0.1 μM to about 50 μM finalconcentration in the wells. Free IGF-1 is at a concentration of about 10nM. Unconjugated insulin is at a concentration of about 1 μM. Controlstreated with no agent, insulin, or IGF-1 or with 5% FCS are alsoconducted.

After 7 days of growth (6 days in the tested chemotherapeutic agents)total and live cell number is determined as described in Example 1.

The IC₅₀ of doxorubicin and each of the conjugates for inhibition ofcell growth is determined under each of the tested conditions. It isdetermined that when administered with insulin or IGF-1, lowerconcentrations of doxorubicin are needed to achieve the same extent ofcell growth inhibition. It is also determined that the IC₅₀s ofdoxorubicin-insulin, doxorubicin-IGF-1, and doxorubicin-IGF-2 are lowerthan or similar to the IC₅₀ of free doxorubicin.

In vivo Testing:

HT29 cells are cultured as described above. Six-week-old female nudemice are injected subcutaneously in the flanks with 10⁷ HT29 cells.Tumors are allowed to grow to a diameter of 5 mm.

When tumors reach a diameter of 5 mm, mice are treated once daily withone of the agents doxorubicin, doxorubicin-insulin, doxorubicin-IGF-1,or doxorubicin-IGF-2. Or the mice are treated with insulin or IGF-1, andthen 30 minutes later with doxorubicin. The mice are fasted for 4 hoursprior to treatment, and are given access to food immediately aftertreatment. Tumor size is measured by calipers twice weekly.

It is found that equal or better tumor shrinkage is achieved with lowerdoses of doxorubicin when the doxorubicin is administered in conjunctionwith insulin, IGF-1, or IGF-2, or when it is administered as part of aconjugate with insulin, IGF-1, or IGF-2. This allows better killing oftumors or allows equivalent killing of tumors with lower side effects.

All patents, patent documents, and references cited herein areincorporated by reference.

1. A compound for treating cancer comprising: an anti-cancerchemotherapeutic agent linked to an insulin-like growth factor-1 (IGF-1)receptor ligand; wherein the IGF-1 receptor ligand is a variant IGF-1that has reduced binding affinity for soluble IGF-1 binding proteinscompared to wild-type IGF-1; wherein the variant IGF-1 comprises thepolypeptide structure A₁-A₂-A₃-A₄-LCG-A₅-A₆-LV-A₇-AL-A₈-A₉-R₁, whereinA1 is FV; A2 is N; A3 is Q; A4 is H; A5 is S; A6 is H; A7 is E; A8 is Y;A9 is L; and R1 is SEQ ID NO:6; provided the variant IGF-1 does notconsist of SEQ ID NO:1.
 2. The compound of claim 1 wherein thechemotherapeutic agent is amsacrine, azacytidine, bleomycin, busulfan,capecitabine, carboplatin, carmustine, chlorambucil, cisplatin,cladribine, cyclophosphamide, cytarabine, dactinomycin, daunorubicin,decarbazine, docetaxel, doxorubicin, epirubicin, estramustine,etoposide, floxuridine, fludarabine, fluorouracil, gemcitabine,hexamethylmelamine, idarubicin, ifosfamide, irinotecan, lomustine,mechlorethamine, melphalan, mercaptopurine, methotrexate, mitomycin C,mitotane, mitoxantrone, oxaliplatin, paclitaxel, pemetrexed,pentostatin, plicamycin, procarbazine, ralitrexed, semustine,streptozocin, temozolamide, teniposide, thioguanine, thiotepa,topotecan, trimitrexate, valrubicin, vincristine, vinblastine,vindestine, or vinorelbine.
 3. The compound of claim 1 wherein thechemotherapeutic agent is an anti-metabolite.
 4. The compound of claim 1wherein the anti-cancer chemotherapeutic agent is linked to the IGF-1receptor ligand by a linkage comprising an amide bond.
 5. The compoundof claim 1 wherein the anti-cancer chemotherapeutic agent is linked tothe variant IGF-1 through an amino group of the variant IGF-1.
 6. Thecompound of claim 3 wherein the anti-metabolite is methotrexate.
 7. Thecompound of claim 1 wherein the anti-cancer chemotherapeutic agent isdoxorubicin.
 8. A pharmaceutical composition comprising a compound ofclaim
 1. 9. A compound for treating cancer comprising: an anti-cancerchemotherapeutic agent linked to an insulin-like growth factor-1 (IGF-1)receptor ligand; wherein the IGF-1 receptor ligand is a variant IGF-1that has reduced binding affinity for soluble IGF-1 binding proteinscompared to wild-type IGF-1; wherein the variant IGF-1 comprises SEQ IDNO:7, SEQ ID NO:8, SEQ ID NO:9, or SEQ ID NO:10.
 10. The compound ofclaim 9 wherein the variant IGF-1 is SEQ ID NO:4.
 11. The compound ofclaim 9 wherein the chemotherapeutic agent is amsacrine, azacytidine,bleomycin, busulfan, capecitabine, carboplatin, carmustine,chlorambucil, cisplatin, cladribine, cyclophosphamide, cytarabine,dactinomycin, daunorubicin, decarbazine, docetaxel, doxorubicin,epirubicin, estramustine, etoposide, floxuridine, fludarabine,fluorouracil, gemcitabine, hexamethylmelamine, idarubicin, ifosfamide,irinotecan, lomustine, mechlorethamine, melphalan, mercaptopurine,methotrexate, mitomycin C, mitotane, mitoxantrone, oxaliplatin,paclitaxel, pemetrexed, pentostatin, plicamycin, procarbazine,ralitrexed, semustine, streptozocin, temozolamide, teniposide,thioguanine, thiotepa, topotecan, trimitrexate, valrubicin, vincristine,vinblastine, vindestine, or vinorelbine.
 12. The compound of claim 9wherein the chemotherapeutic agent is an anti-metabolite.
 13. Thecompound of claim 9 wherein the anti-cancer chemotherapeutic agent islinked to the IGF-1 receptor ligand by a linkage comprising an amidebond.
 14. The compound of claim 9 wherein the anti-cancerchemotherapeutic agent is linked to the variant IGF-1 through an aminogroup of the variant IGF-1.
 15. The compound of claim 12 wherein theanti-metabolite is methotrexate.
 16. The compound of claim 9 wherein theanti-cancer chemotherapeutic agent is doxorubicin.
 17. pharmaceuticalcomposition comprising a compound of claim 9.